Obstructive sleep apnea hypopnea syndrome (OSAHS) is an important medical condition which causes significant morbidity and mortality. The prevalence of OSAHS in Spain is 4-6% in men and 2-4% in women and rises steadily with age. Snoring and smoking have been independently linked, and smoking may be a risk factor for developing OSAHS. This is particularly true of heavy smokers (> 2 packs/day), those at greatest risk for LC. Associations between OSAHS and some forms of cancer have been described in humans, especially in those experiencing nocturnal hypoxemia, and intermittent hypoxia has been linked to the progression of cancer in animal models. LC is currently the leading cause of cancer deaths in developped nations. A link between OSAHS and LC, therefore, is plausible.